Method for the obtaining cost effective powder

Abstract

A production method of particulate materials, through centrifugal atomization (CA) is disclosed. The method is suitable for obtaining fine spherical powders with exceptional morphological quality and extremely low content, or even absence, of nonspherical shape particles and internal voids. An appropriate cost effective method for industrial scale production of metal alloy, intermetallic, metal matrix composite or metal-like material powders in large batches is also disclosed. The atomization technique can be extended to other than the centrifugal atomization with rotating element techniques.

The invention claimed is: 
     
       1. A method for producing metal based alloy powders by means of centrifugal atomization in a closed chamber comprising the steps of:
 a) providing a composition comprising at least one metal, 
 b) melting the composition, and 
 c) atomizing the molten composition by means of centrifugal atomization with an atomizing disk; 
 wherein the atmosphere in the dosed atomization chamber is pressurized and/or cooled; and wherein the contact angle between the molten composition and the atomizing disk is above 96° and smaller than 168°, measured using the sessile drop method. 
 
     
     
       2. The method according to  claim 1 , wherein the molten composition is over-heated at a temperature of at least 52° C. above Tm and below 396° C.+Tm, Tm being the melting temperature of the composition to be atomized in degree Celsius (° C.). 
     
     
       3. The method according to  claim 1 , wherein the atomizing disk is ceramic and is supported by a metallic cage structure. 
     
     
       4. The method according to  claim 1 , wherein the atomization chamber comprises at least one bearing with an angular contact of 15.5° or more and 34° or less. 
     
     
       5. The method according to  claim 1 , wherein the atomization chamber comprises at least one bearing comprising at least one ring, wherein the hardness of the ring is 54 HRc or more after being exposed at 85° C. or more during 35 minutes or more. 
     
     
       6. The method according to  claim 1 , wherein the surface tension between the molten composition and the atomizing disk surface is above 780 mN/m and below 1750 mN/m measured using the sessile drop method. 
     
     
       7. The method according to  claim 1 , wherein the atomization chamber comprises an oxygen trap and the oxygen content is maintained below 280 ppm by volume before the atomization starts. 
     
     
       8. The method according to  claim 1 , wherein the composition provided in step a) is selected from an iron-based alloy, an aluminum-based alloy, a nickel-based alloy, a copper-based alloy, a cobalt-based alloy, a magnesium-based alloy, a silver-based alloy, a germanium-based alloy, a gold-based alloy and/or a lithium-based alloy. 
     
     
       9. The method according to  claim 1 , wherein vacuum is applied in the chamber once the metal has been molten and previous to atomization. 
     
     
       10. The method according to  claim 1 , wherein the melting chamber comprises at least one oxygen trap. 
     
     
       11. The method according to  claim 1 , wherein a cooling gas is introduced in the atomization chamber during the atomization process. 
     
     
       12. A method for producing, metal-based alloy powders by means of centrifugal atomization in a closed chamber comprising the steps of:
 a) providing a composition comprising at least one metal, 
 b) melting the composition, and 
 c) atomizing the molten composition by means of centrifugal atomization with an atomizing disk; 
 wherein the atmosphere in the closed atomization chamber is pressurized and/or cooled, and wherein the atmosphere in the chamber is modified by introducing a gas and/or a liquid, trapping the oxygen, changing the temperature and/or changing the pressure, so that there is an increase of surface tension between the molten composition and the atomizing disk which is at least 55 mN/m with respect to the surface tension in air. 
 
     
     
       13. The method according to  claim 12 , wherein the molten composition is over-heated at a temperature of at least 52° C. above m and below 396° C. +Tm, Tm being the melting temperature of the composition to be atomized in degree Celsius (° C.). 
     
     
       14. The method according to  claim 12 , wherein the atomizing disk is ceramic and is supported by a metallic cage structure. 
     
     
       15. The method according to  claim 12 , wherein the atomization chamber comprises at least one bearing with an angular contact of 15.5° or more and 34° or less. 
     
     
       16. The method according to  claim 12 , wherein the atomization chamber comprises at least one hearing comprising at least one ring, wherein the hardness of the ring is 54 HRc or more after being exposed at 85° C. or more during 35 minutes or more. 
     
     
       17. The method according to  claim 12 , wherein the surface tension between the molten composition and the atomizing disk surface is above 780 mN/m and below 1750 mN/m measured using the sessile drop method. 
     
     
       18. The method according to  claim 12 , wherein the atomization chamber comprises an oxygen trap and the oxygen content is maintained below 280 ppm by volume before the atomization starts. 
     
     
       19. The method according to  claim 12 , wherein the composition provided in step a) is selected from an iron-based alloy, an aluminum-based alloy, a nickel-based alloy, a copper-based alloy, a cobalt-based alloy, a magnesium-based alloy, a silver-based alloy, a germanium-based alloy, a gold-based alloy and/or a lithium-based alloy. 
     
     
       20. The method according to  claim 12 , wherein a cooling gas is introduced in the atomization chamber during the atomization process.